A Zero Added Loss Multiplexing (ZALM) Source Simulation

TL;DR

This work introduces ZALM, a broadband, memory-loading entanglement source, and a modular NetSquid-based simulator that exposes 20+ tunable parameters to explore how SPDC bandwidth, DWDM grid spacing, and heralding affect fidelity and entangled bits per use over distance. It provides a detailed model of SPDC, four-qubit state generation, HOM visibility, DWDM filtering, and post-processing, and demonstrates trade-offs between fidelity and throughput under realistic losses. Key findings show that fidelity can be maintained while increasing rate by narrowing SPDC degeneracy bandwidth and employing photon-number resolving detectors; in ideal mode fidelity remains high though the ebit rate decays with distance, highlighting the role of classical signaling latency. The tool serves as a building block for end-to-end quantum network studies, enabling co-design of source, filtering, and feedforward settings for specific memories and network architectures.

Abstract

Zero Added Loss Multiplexing (ZALM) offers broadband, per channel heralded EPR pairs, with a rich parameter space that allows its performance to be tailored for specific applications. We present a modular ZALM simulator that demonstrates how design choices affect output rate and fidelity. Built in NetSquid with QSI controllers, it exposes 20+ tunable parameters, supports IDEAL and REALISTIC modes, and provides reusable components for Spontaneous Parametric Down Conversion (SPDC) sources, interference, Dense Wavelength Division Multiplexing (DWDM) filtering, fiber delay, active polarization gates, detectors, and lossy fiber. Physics based models capture Hong Ou Mandel (HOM) visibility, insertion loss, detector efficiency, gate errors, and attenuation. Using this tool, we map trade offs among fidelity, link distance, and entangled pairs per use, and show how SPDC bandwidth and DWDM grid spacing steer performance. Using the default configuration settings, average fidelity emains constant at 0.8 but the ebit rate decreases from 0.0175 at the source to 0.0 at 50 km; narrowing the SPDC degeneracy bandwidth increases the ebit rate significantly without affecting fidelity. The simulator enables codesign of source, filtering, and feedforward settings for specific quantum memories and integrates as a building block for end to end quantum network studies.

Figures (7)

• Figure 1: ZALM source components.
• Figure 2: SPDC configuration options.
• Figure 3: Optical setup to determine which Bell state is detected.
• Figure 4: Fidelity / Bits per use vs Configuration
• Figure 5: Fidelity, ebits per use vs Distance, IDEAL setting